Magnetoresistance From Quantum Interference Effects in Ferromagnets

摘要

The desire to maximize the sensitivity of read/write heads and thus theinformation density of magnetic storage devices has produced an intenseinterest in the magnetoresistance (MR) of magnetic materials. Recentdiscoveries include "colossal" MR of the manganites1-4 and the enhanced MR oflow carrier density ferromagnets4-6. In the low carrier density systemsinvestigated to date as well as the manganites, a key feature is that theelectrical conduction is due to a different set of electrons than the localizedelectrons responsible for the magnetism. Here we propose a mechanism forferromagnetic MR originating from quantum interference effects, rather thansimple scattering. The new mechanism obtains in disordered low carrier densitymagnets where the magnetism as well as the electrical conduction are due to thesame electrons. Here the MR is positive and only weakly temperature dependentbelow the Curie point. This is very different from the MR seen when conductionelectrons and local moments can be treated separately, in which case the MR isnegative and strongly peaked at the Curie point.